1. Field of the Invention
The present invention relates to a gear shift time automatic adjusting apparatus in an automatic transmission in which a gear shift time in the automatic transmission can be automatically adjusted when the automatic transmission or a control unit (controller) is replaced.
2. Description of the Related Art
A gear shift time automatic adjusting apparatus in an automatic transmission in the prior art is disclosed, for example, in Japanese Patent Laid Open Publication Hei No. 5-99308 (hereinafter, referred to as a "first prior art example) and in Japanese Patent Laid Open Publication Hei No. 1-169164 (hereinafter, referred to as a "second prior art example).
The first prior art example was proposed by the applicant of the present application previously, and in the case where the automatic transmission is brand new, in order to achieve a gear shift in a set required time and to prevent elongation of the gear shift time as well as gear shift shock even when the lapping of friction materials constituting engaging elements is insufficient, a gear shift load applied to the engaging elements is detected, for example by detecting a throttle opening degree, and by accumulating this gear shift load, it is judged that the lapping of the friction materials is insufficient as long as the accumulated gear shift load is small, and an engaging oil pressure of initial characteristic having a higher oil pressure characteristic than a normal condition is applied to compensate for the insufficient lapping of the friction material. Here in the specification, the lapping means to lap or rub the pair of engaging elements, i.e., friction materials with other. In this case, when the lapping is sufficient, i.e., the friction materials are adapted sufficiently, the coefficient of friction of the friction materials is large, and when the lapping is insufficient, i.e., the friction materials are not adapted sufficiently, the coefficient of friction is small.
Furthemore, in the second prior art example, on the basis of an input rotational speed and an output rotational speed of a gear shift gear mechanism during gear shift, an inertia phase time representing a time during which a gear ratio representing a ratio between the input and the output rotational speed is measured at each throttle opening degree by inertia phase time measuring means. A line pressure during gear shift is controlled by line pressure regulating means so that the measured inertia phase time reaches a target value to thereby perform the so-called learning control which copes with the non-uniformity of line pressure control parts and the deterioration with age of the friction materials.
However, in the first prior art example, it is intended to control the engaging oil pressure supplied to the engaging elements on the basis of the accumulated gear shift load value. However, since the accumulated gear shift load value is managed by a controller which is independent of the automatic transmission, when this controller is replaced or the automatic transmission is replaced, an accumulated gear shift load value of a new controller will be different from the value of the previous controller, and thus, it is necessary to modify the accumulated gear shift load value of the new controller to coincide with the previous value. However, this is not only troublesome but also the modification is sometimes forgotten, and satisfactory engaging oil pressure control according to a correct accumulated gear shift load value may not be achieved in some cases. Furthermore, there is another unsolved problem in which it is impossible to cope with the non-uniformity and the deterioration with age of the coefficient of friction of the friction materials of the engaging elements, and the gear shift time will be deviated from a preset gear shift time.
Also, in the second prior art example, the learning control is performed so that an inertia phase time during which a gear ratio is changing coincides with a target value. However, since this learning control is carried out at each throttle opening degree, a fine correction can be made. On the other hand, since the learning is not performed as often at a throttle opening degree whose frequency of occurrence is small, unsolved problem is involved in which optimum control cannot be achieved. Furthermore, in the learning control, on the basis of a current deviation of the gear shift time, the oil pressure of the next time will be corrected, and thus although it is possible to cope with the deterioration with age (gradual change) of the friction materials, it is impossible to cope with large deterioration with age such as insufficient lapping as in the initial time of starting the use of the automatic transmission, and the gear shift time will be deviated from the set gear shift time.